The RAF had Gunnery Officers from the start of the war: although I don't know for sure I'd expect every bomber squadron to have an officer whose responsibility was the squadron's gunnery. I'd not expect every such officer to have risen from the ranks in the pre-war RAF, but maybe.

Stories from the USAAF's famous low-level raid on Ploesti describe the benefits of having an experienced RAF Gunnery Officer with them, not least as acting as a fire controller.

In accordance with orders contained in Form B.357, 628 aircraft departed England for this raid on Mannheim; 32 aircraft were lost to include Lancaster JA 708 P. At the time of its loss the aircraft had a total of 103 hours of flying time. Also lost from 97 Squadron were the crew of W/O Stevenson. This crew was briefed to be one of 97 Squadron’s 16 aircraft detailed to attack Mannheim. The crew’s bomb load consisted of 1 x 4,000 lb. bomb, 5 x 1,000 lb. bombs and 4 x 250 lb. markers.

97 Squadron’s Gunnery Officer S/L McKinna and the squadron’s Navigational Officer S/L Foster joined the crew for this operation. McKinna and Foster replaced Dunn and White who were tour expired as would the whole crew have been at the conclusion of this operation. On arrival at the target the crew found clear skies and good visibility.

The crew had settled down on their bombing run when they were picked up by a blue tinged, radar controlled, master searchlight and were immediately coned by an estimated 10 other searchlights. The airmen were committed to their run in with Bomb Aimer Beesley releasing the markers and bombs at 2145 hours. Pilot Fletcher then immediately put the aircraft through the most violent corkscrew descent the crew had ever experienced. Despite his efforts Fletcher could not lose the searchlights, but suddenly all of the searchlights were switched off simultaneously.

Fletcher then proceeded to climb the aircraft in order to regain the altitude lost during the evasive manoeuvres. Two minutes after releasing their bombs they were attacked by a Messerschmitt BF110 night fighter piloted by Unteroffizie Josef Brunner operating out of Venlo in Holland. Brunner who was working in coordination with the searchlight crews had followed the aircraft down in its attempts to evade the searchlights.

With the aircraft on fire Fletcher gave the order to bail out, however this command was not heard by Layne due to the intercom system having been put out of action. One of the bomb aimers duties was to remove the square emergency hatch in the nose section that enabled the crew to leave the aircraft in the case of an in flight emergency. Removing the hatch Sgt. Beesley exited the aircraft followed immediately by Nelson and Fletcher.

Wireless Operator Layne recalled later “ I took off my earphones and went to see if I could help but the back of the aircraft was an inferno.” Layne could see the mid upper gunners slumped body silhouetted against the searchlights in his shattered turret and the same fate had befallen the rear gunner.

Retrieving his parachute from its place of stowage Wally Layne scrambled to the front of the aircraft and found the cockpit empty, he was the only man alive in an aircraft that was in a long dive trailing flames behind it. As he scrambled, in total darkness, to the front of the aircraft Wally Layne managed to secure one clip of his parachute to the D ring on his harness. However the second clip was proving difficult. With his feet dangling in space from the bomb aimers emergency hatch Wally frantically fiddled with the second clip until it suddenly clipped into place.

Throwing himself from the doomed Lancaster Layne exited by the bomb aimers hatch and immediately deployed his parachute. At almost the same moment his parachute opened and deposited him in a small clearing in the forest not far from away from the burning remains of his aircraft. Having sustained no physical damages beyond a jarring of his heels, Wally left his parachute hanging in a tree and prepared for life as an evader.